The direct functionalization of heterocyclic compounds has emerged as one of the most important topics in the field of metal-catalyzed C-H bond activation due to the fact that products are an important synthetic motif in organic synthesis, the pharmaceutical industry, and materials science. This critical review covers the recent progresses on the regioselective dehydrogenative direct coupling reaction of heteroarenes, including arylation, olefination, alkynylation, and amination/amidation mainly utilizing transition metal catalysts (113 references). 相似文献
Light‐guiding core/sheath fibers are fabricated from two different refractive index (RI) polymers by coaxial electrospinning. The morphology and fiber diameter are analyzed with scanning electron and fluorescence microscopies. It is found that the diameter of the core and the thickness of the sheath could be varied from 100 to 400 nm by changing the concentration of the outer solution. The incorporation of a chromophore into the inner material confirmed the uniformity of the core/sheath structure in long segments of the fibers. The boundary is clearly seen: the core diameter and the thickness of the sheath are constant along the fiber axis in fluorescence images. The ejected beam is circular and light‐guided along the fiber axis as in an optical fiber.
Oxidative coupling reaction of 1‐hexyl–3,4‐dimethylpyrrole affords a conjugated conducting poly(1‐hexyl‐3,4‐dimethyl‐2,5‐pyrrolylene) (PHDP), which is completely soluble in common organic solvents. The luminescence of PHDP is comparable to that of poly(N‐vinylcarbazole) (PVK), which has been widely used in electroluminescence devices. The quantum efficiency of PHDP is 2.5 times higher than that of PVK. A rationalization is presented relating the conductivity of PHDP to its polymer structure. 相似文献
The photoirradiation of trans‐ and cis‐poly(dimethylsilylenephenylenevinylene)s gave cis‐rich mixtures at equilibrium states. The degree of the photoisomerization could be exactly evaluated by comparing the UV spectra of the photoirradiated solutions with those of the trans and cis polymers. The geometric configuration of the trans and cis polymers was thermally stable and hardly changed even though they were heated. The trans and cis polymers exhibited different emission properties; e.g., trans polymer: λmax = 400 nm, quantum yield = 3.4×10–3; cis polymer: λmax = 380 nm, quantum yield = 1.5×10–3. 相似文献
A new class of near-infrared (NIR) fluorophores, PAI , is obtained by consecutive C−N/C−C bond formation between diphenylamines and 9,10-dibromoperylenecarboximide. Owing to the rigid structure, extended π-conjugation and pronounced push-pull substitution, these fluorophores show emission maxima up to 804 nm and large Stokes shifts. The extraordinarily high fluorescence quantum yields from 47 % to 70 % are attributed to chloro substitution in the bay positions of the perylene core. These characteristics, together with high photostability, qualify them as useful NIR emitters for applications as biomarkers and security inks. 相似文献
Covalent organic frameworks have recently shown high potential for photocatalytic hydrogen production. However, their structure-property-activity relationship has not been sufficiently explored to identify a research direction for structural design. Herein, we report the design and synthesis of four benzotrithiophene (BTT)-based covalent organic frameworks (COFs) with different conjugations of building units, and their photocatalytic activity for hydrogen production. All four BTT-COFs had slipped parallel stacking patterns with high crystallinity and specific surface areas. The change in the degree of conjugation was found to rationally tune the rate of photocatalytic hydrogen evolution. Based on the experimental and calculation results, the tunable photocatalytic performance could be mainly attributed to the electron affinity and charge trapping of the electron accepting units. This study provides important insights for designing covalent organic frameworks for efficient photocatalysts. 相似文献